[UBSan] Do not overwrite the default print_summary sanitizer option.

Summary:
This option is true by default in sanitizer common. The default
false value was added a while ago without any reasoning in
https://github.com/llvm-mirror/compiler-rt/commit/524e934112a593ac081bf2b05aa0d60a67987f05

so, presumably it's safe to remove for consistency.

Reviewers: hctim, samsonov, morehouse, kcc, vitalybuka

Reviewed By: hctim, samsonov, vitalybuka

Subscribers: delcypher, #sanitizers, llvm-commits, kcc

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D67193

llvm-svn: 371442